JP2000107999A - Wafer chamfering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer chamfering method which can process the upper and the lower surface widths even in a lapping process. SOLUTION: A chamfering process is carried out to position the center P in the thickness direction of the peripheral edge of a wafer W at the center M of the grinding groove 110 of an outer periphery grinding wheel 108 constantly. The wafer W is ground evenly at the upper side and the lower side, and when a lapping process is carried to the wafer W, the process is carried out to make thinner evenly to the upper side and the lower side, from the thick part of the wafer W, and as a result, the wafer W is made in the even surface widths at the upper side and the lower side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wafer chamfering method, and more particularly to a wafer chamfering method for chamfering a peripheral edge of a wafer made of a hard brittle material such as silicon.

[0002]

2. Description of the Related Art A wafer sliced from a state of an ingot by a cutting machine such as a wire saw is chamfered at its periphery in order to prevent chipping and cracking. In this chamfering process, as shown in FIG. 13, the grindstone 2 having the V-shaped groove 1 formed on the peripheral surface is rotated, and the periphery of the wafer W held on the chuck table 3 is inserted into the groove 1 of the grindstone 2. This is done by contact.

The wafer W is chamfered as described above. At this time, the wafer W is processed so that the width of the portion to be chamfered (hereinafter referred to as "surface width") is constant. There is a need. In this case, if the wafer has a uniform thickness, as shown in FIG.
Is processed by positioning the grindstone 2 and the wafer W such that the center in the thickness direction of the grindstone 2 is positioned at the center of the groove 1 of the grindstone 2 so that the surface width becomes constant over the entire circumference of the wafer W. can do.

[0004] However, the thickness of the wafer cut by the cutting machine is not always uniform, and is often uneven as shown in FIG. For this reason, conventionally,
As shown by the two-dot broken line in FIG.
It was processed assuming _A. That is, conventionally, the thickness of the peripheral portion of the wafer W is measured at three to five points, and the average value (maximum value or minimum value depending on the case) is defined as the wafer thickness T _A, and the wafer W _A having a uniform thickness is measured. And processed in the same manner as above.

[0005]

However, when the wafer W having an uneven thickness as described above is processed on the assumption that the wafer W is uniform, the surface width C varies as shown in FIG. Occurs. Then, when lapping, which is the next step, is performed in this state, the lapping is performed so that the wafer W is processed to be uniformly thinned in the vertical direction from a thick portion, so that the upper and lower surface widths are uneven as shown by the dotted line in FIG. Wafer W
There is a disadvantage that it is processed into _R.

Normally, the chuck table 3 for holding the wafer W is processed on the assumption that there is no runout at the outer periphery. The fluctuation of the chuck table 3 causes variations in the surface width of the wafer W. When wrapping the wafer W, there is a disadvantage that the same up and down in the plane width from being processed into non-uniform wafer W _R.

The present invention has been made in view of such circumstances, and has as its object to provide a wafer chamfering method capable of uniformly processing upper and lower surface widths in a lapping process.

[0008]

According to a first aspect of the present invention, in order to achieve the above object, a grindstone having a V-shaped groove formed on a peripheral surface thereof is rotated, and the groove is held by a chuck table. In the wafer chamfering method of chamfering the peripheral edge of the wafer by rotating the peripheral edge of the wafer by abutting, the center in the thickness direction of the peripheral edge of the wafer abutting on the groove of the whetstone is the groove of the whetstone. The method is characterized in that the wafer is rotated and chamfered while adjusting the relative position of the grindstone and the wafer in the axial direction so as to be located at the center.

According to the present invention, chamfering is performed by bringing the periphery of the wafer into contact with the groove of the grindstone so that the center of the periphery of the wafer in the thickness direction is always located at the center of the groove of the grindstone.
If the wafer processed in this way is wrapped, the lapping is processed so as to be uniformly thinned from a thick portion of the wafer, so that the wafer can be processed into a wafer having a uniform upper and lower surface width.

According to a fifth aspect of the present invention, in order to achieve the above object, a grindstone having a groove having a trapezoidal cross section formed on a peripheral surface thereof is rotated, and is held on a chuck table on an inclined surface on one side of the groove. By rotating the one-sided peripheral edge of the wafer in contact with the wafer, the one-sided peripheral edge of the wafer is chamfered, and the other side of the wafer held by the chuck table on the inclined surface on the other side of the groove. A wafer chamfering method in which the periphery of the wafer is chamfered and the periphery of the wafer is chamfered by rotating the periphery of the wafer by abutting the periphery of the wafer, wherein the grinding wheel is moved from the center in the thickness direction of the periphery of the wafer. The wafer is rotated while adjusting the relative position of the grindstone and the wafer in the axial direction so that the distance to the inclined surface of the groove becomes constant, and both sides of the periphery of the wafer are adjusted. Characterized by chamfered.

According to the present invention, the peripheral edge of the wafer is brought into contact with the inclined surface of the groove of the grinding stone so that the distance from the center in the thickness direction of the peripheral edge of the wafer to the inclined surface of the groove of the grinding stone becomes constant. Chamfering. If the wafer processed in this way is wrapped, the lapping is processed so as to be uniformly thinned from a thick portion of the wafer, so that the wafer can be processed into a wafer having a uniform upper and lower surface width.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a wafer chamfering method according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a plan view showing a configuration of a wafer chamfering apparatus to which a wafer chamfering method according to the present invention is applied. As shown in FIG. 1, the wafer chamfering apparatus 10 includes a thickness measuring unit 20, a transfer unit 30, a processing unit 40, and a control unit (not shown).

The thickness measuring section 20 measures the thickness of the outer peripheral portion of the wafer W to be chamfered. The thickness measuring unit 20 includes a measuring table 22 and a thickness sensor 24. The measurement table 22 holds the central portion of the back surface of the wafer W by vacuum suction. Then, the held wafer W
Is rotated around the central axis. The thickness sensor 24 includes a pair of capacitance sensors (not shown). The pair of capacitance sensors are arranged so as to face each other at a predetermined interval in the vertical direction, and measure the distance to the front surface and the back surface of the wafer W arranged therebetween.

Here, when the wafer W to be chamfered is placed on the measurement table 22, one point near its outer peripheral portion is arranged between the capacitance sensors. The capacitance sensor measures the distance between the front surface and the back surface of the wafer W. The measured value is output to the arithmetic unit of the control unit, and the arithmetic unit obtains the thickness of the outer peripheral portion of the wafer W by arithmetic processing.

In the thickness T, the distance between the upper capacitance sensors is L, the distance from the upper capacitance sensor to the surface of the wafer W is S ₁ , and the lower capacitance sensor is S. If the distance from to the back surface of the wafer W is S ₂ ,

[0016]

T = L− (S ₁ + S ₂ ) The transport unit 30 is provided between the thickness measuring unit 20 and the processing unit 40.
Is transferred to the wafer W. The transfer section 30 includes a transfer arm 32 for holding the wafer W, and a slide block 34 for slidingly moving the transfer arm 32.

The transfer arm 32 has a vertically movable suction pad 36 at the lower end thereof, and the suction pad 36 holds the wafer W by vacuum suction of the upper surface of the wafer W. On the other hand, the slide block 34 moves on the guide rail 38 to move the transfer 32 horizontally. The processing unit 40 performs chamfering of the wafer W. The processing unit 40 includes a wafer feed unit 42 and a grinding unit 44, as shown in FIGS.

First, the configuration of the wafer feeding unit 42 will be described. As shown in FIG. 2, a pair of Y-axis guide rails 5 are provided on a base plate 50 disposed horizontally.
2, 52 are laid at predetermined intervals. A Y-axis table 56 is slidably supported on the pair of Y-axis guide rails 52 via Y-axis linear guides 54, 54,.

The nut member 5 is provided on the lower surface of the Y-axis table 56.
The nut member 58 is fixed to the pair of Y members.
It is screwed into a Y-axis ball screw 60 disposed between the axis guide rails 52, 52. Both ends of the Y-axis ball screw 60 are rotatably supported by bearing members 62, 62 disposed on the base plate 50, and one end of the Y-axis ball screw 60 provided on one bearing member 62. Motor 64
Output shafts are connected. The Y-axis ball screw 60 is rotated by driving the Y-axis motor 64. As a result, the Y-axis table 56 is
Slide horizontally along 2.

As shown in FIG. 2 and FIG. 3, the pair of Y-axis guide rails 52, 5
2 and a pair of X-axis guide rails 66
Is laid. This pair of X-axis guide rails 66,
On X 66, X-axis linear guides 68, 68,.
A shaft table 70 is slidably supported. A nut member 72 is fixed to the lower surface of the X-axis table 70, and the nut member 72 is attached to the pair of X-axis guide rails 6.
It is screwed to an X-axis ball screw 74 disposed between the first and second X-ray balls 6 and 66. Both ends of the X-axis ball screw 74 have the X
It is rotatably supported by bearing members 76, 76 disposed on a shaft table 70, and one end thereof is connected to an output shaft of an X-axis motor 78 provided on one bearing member 76. . The X-axis ball screw 74 is rotated by driving the X-axis motor 78. As a result, the X-axis table 70 slides horizontally along the X-axis guide rails 66.

As shown in FIGS. 2 and 3, a Z-axis base 80 is vertically provided on the X-axis table 70, and a pair of Z-axis guide rails 8 are provided on the Z-axis base 80.
2, 82 are laid at predetermined intervals. A Z-axis table 86 is slidably supported on the pair of Z-axis guide rails 82 via Z-axis linear guides 84, 84.

The nut member 8 is provided on the side of the Z-axis table 86.
The nut member 88 is fixed to the pair of Zs.
It is screwed into a Z-axis ball screw 90 provided between the axis guide rails 82,82. The Z-axis ball screw 90 has a bearing member 9 whose both ends are disposed on the Z-axis base 80.
2, 92, the lower end of which is connected to the output shaft of a Z-axis motor 94 provided on the lower bearing member 92. The Z-axis ball screw 90 is rotated by driving the Z-axis motor 94. As a result, the Z-axis table 86 slides vertically along the Z-axis guide rails 82.

On the Z-axis table 86, a θ-axis motor 9
6 are installed vertically. A θ-axis shaft 98 is connected to the output shaft of the θ-axis motor 96, and a chuck table 100 is horizontally fixed to the upper end of the θ-axis shaft 98. The wafer W to be chamfered is placed on the chuck table 100 and held by vacuum suction. The held wafer W is rotated around the θ-axis by driving the θ-axis motor 96.

In the wafer feeding unit 42 configured as described above, the chuck table 100 is horizontally moved in the Y direction in the figure by driving the Y-axis motor 64 and is driven by driving the X-axis motor 78 in the figure. Move horizontally in the X direction. Then, the Z-axis motor 94 is driven to move vertically in the Z direction in the figure, and the θ-axis motor 96 is driven to rotate around the θ-axis.

Next, the configuration of the grinding unit 44 will be described. As shown in FIGS. 2 and 3, a gantry 102 is installed vertically on the base plate 50. An outer peripheral motor 104 is installed vertically on the gantry 102, and an outer peripheral spindle 106 is connected to an output shaft of the outer peripheral motor 104. The outer peripheral grinding wheel 108 for chamfering the peripheral edge of the wafer W
6 and is rotated by driving the outer peripheral motor 104.

Here, a grinding groove 110 having a V-shaped cross section, which is the same as the chamfered shape required for the wafer W, is formed on the outer periphery of the outer peripheral grinding wheel 108 (total grinding wheel). By contacting the peripheral edge of W, the peripheral edge of wafer W is chamfered. The control unit (not shown) controls the processing unit 40 based on the measurement result of the thickness measurement unit 20.
To perform chamfering of the wafer W.

Next, a wafer chamfering method according to the present invention using the wafer chamfering apparatus 10 configured as described above will be described. First, the transfer arm 32 of the transfer unit 30 receives a wafer W from a wafer supply device (not shown). The transfer arm 32 transports the wafer W to the thickness measuring unit 20 and places it on the measurement table 22. The measurement table 22 suction-holds the placed wafer W.

One point near the outer periphery of the wafer W held on the measurement table 22 is located at the measurement point of the thickness sensor 24 (between a pair of capacitance sensors constituting the thickness sensor 24). Do). The thickness sensor 24 measures the thickness at one point near the outer peripheral portion. The thickness of the wafer W thus obtained is referred to as “thickness T ₀ ” as the thickness when the angle is 0 °.

When the measurement of the thickness T ₀ is completed, the control device rotates the measuring table 22 by 45 ° in the clockwise direction. Then, the thickness of the wafer W stopped at that position is measured by the thickness sensor 24. The thickness of the wafer W obtained in this manner is defined as the thickness at an angle of 45 ° as “thickness T
₄₅ ”. When the measurement of the thickness T ₄₅ is completed, the control device causes the 45 ° rotation of the measurement table 22 in a clockwise direction again. Then, the thickness of the wafer W stopped at that position is measured by the thickness sensor 24. The thickness of the wafer W thus obtained is referred to as “thickness T ₉₀ ” as the thickness at an angle of 90 °.

Hereinafter, angles 135 ° and 180 ° are obtained in the same manner.
°, 225 °, 270 °, 315 ° wafer W
"Thickness T near the outer periphery of₁₃₅], “Thickness T₁₈₀], [Thickness
Sa T ₂₂₅], “Thickness T₂₇₀], “Thickness T₃₁₅Measure
(See FIG. 4A). Thickness obtained as above
The measured data of T is plotted with thickness T on the vertical axis and rotation angle θ on the horizontal axis.
Plot on a graph. And connect each point with a straight line
And a graph as shown in FIG.

After completing the measurement of the thickness T ₃₁₅ , the control device of the control section rotates the measuring table 22 by 45 ° in the clockwise direction. This causes the wafer W to make exactly one rotation and return to the original position. Thereby, the thickness is measured. When the thickness measurement is completed, the transfer arm 32 receives the wafer W from the measurement table 22 (not shown). The transfer arm 32 transfers the wafer W to the processing unit 40.
And placed on the chuck table 100. The chuck table 100 suction-holds the placed wafer W. The center of the wafer W held on the chuck table 100 matches the center of the chuck table 100.

At this time, the chuck table 100 receives the wafer W in a state where it is located at a predetermined origin position. That is, the rotation axis θ is located on the Y axis, and the wafer W is received at a position separated from the outer peripheral grinding wheel 108 by a predetermined distance. Also, chuck table 1
00 receives the wafer W in a state where it is positioned at a predetermined height with respect to the outer peripheral grinding wheel 108. That is, FIG.
As shown in (a), the chuck table 100 receives the wafer W with its upper surface U located at a distance D from the center M of the grinding groove 110 of the outer peripheral grinding wheel 108.

When the wafer W is held on the chuck table 100, a controller (not shown) performs positioning of the wafer W in the thickness direction based on the measurement result of the thickness sensor 24. That is, the wafer W is positioned in the thickness direction such that the center of the wafer W in the thickness direction coincides with the center of the grinding groove 110 of the outer peripheral grinding wheel 108. This positioning is performed as follows.

As shown in FIG. 5A, the thickness measuring section 20
The wafer W immediately after being transported from the chuck table 100 is held on the chuck table 100 in a state where the center P in the thickness direction is shifted from the center M of the grinding groove 110 of the outer peripheral grinding wheel 108. Here, when the angle is 0 °, that is, the thickness T ₀ of the wafer W at the grinding start point is known from the measurement result of the thickness sensor 24 (the wafer W is moved in parallel and the chuck is moved from the measurement table 22 to the chuck. Since it is transported to the table 100, the angle 0 measured by the thickness sensor 24 is zero.
The thickness T ₀ of the wafer W at ° corresponds to the thickness T ₀ of the wafer W at the grinding start point. ). This indicates that the center P ₀ in the thickness direction of the wafer W is located at (T _0/2 ) from the upper surface U of the chuck table 100.

On the other hand, as described above, the upper surface U of the chuck table 100 has the grinding groove 1 of the outer peripheral grinding wheel 108.
The wafer W is received in a state where the wafer W is positioned at a distance D from the center M of the wafer 10. Therefore, the deviation amount δ between the center P ₀ in the thickness direction of the wafer W and the center M of the grinding groove 110 of the outer peripheral grinding wheel 108 is:

[0036]

It can be seen that δ = D− (T _0/2 ). The control device drives the Z-axis motor 94 to raise the chuck table 100 by the distance δ. Thereby, as shown in FIG. 5B, the center P ₀ in the thickness direction of the wafer W is located at the center M of the grinding groove 110 of the outer peripheral grinding wheel 108.

Thus, the positioning of the wafer W in the thickness direction is completed. Thereafter, the chamfering of the wafer W is started. First, the outer peripheral motor 104 is driven,
The outer peripheral grinding wheel 108 rotates at high speed. When the rotation of the outer peripheral grinding wheel 108 is stabilized, the Y-axis motor 6
4 is driven, and the wafer W is sent to the outer peripheral grinding wheel 108.

When the wafer W is fed a predetermined distance, the peripheral edge of the wafer W comes into contact with the grinding groove 110 of the outer peripheral grinding wheel 108. After the contact, the wafer W is sent slowly toward the outer peripheral grinding wheel 108, and as a result, the peripheral edge of the wafer W is ground by the outer peripheral grinding wheel 108 and chamfered. The wafer W is fed until the axial distance between the outer peripheral grinding wheel 108 and the wafer W reaches a predetermined set distance. When the inter-axis distance reaches a predetermined distance, the Y-axis motor 64
Is stopped.

When the feed in the Y-axis direction is stopped, then θ
The shaft motor 96 is driven, and the wafer W starts to rotate slowly around the θ axis in the direction opposite to the outer peripheral grinding wheel 108.
As a result, the position of the peripheral edge of the wafer W in contact with the grinding groove 110 of the outer peripheral grinding wheel 108 changes, and the peripheral edge of the wafer W is chamfered sequentially. However, as described above, since the thickness of the wafer W varies depending on the position of the peripheral edge, when the wafer W is rotated as described above, the center P in the thickness direction of the wafer W at the point of contact with the grinding groove 110 is formed. In addition, there is a problem that the grinding groove 110 is displaced from the center M.

Therefore, the wafer W is moved in the axial direction at the same time as the rotation of the wafer W, whereby the center P of the wafer W in the thickness direction is controlled to be always located at the center M of the grinding groove 110. Specifically, control is performed as follows. From the measurement result by the thickness sensor 24, the rotation angle 45
°, 90 °, 135 °, 180 °, 225 °, 270
°, the thickness T of the peripheral edge of the wafer W at 315 °
₄₅ , T ₉₀ , T ₁₃₅ , T ₁₈₀ , T ₂₂₅ , T ₂₇₀ , T ₃₁₅ are known. Therefore, the wafer W is set at 45 °, 90 °
°, 135 °, 180 °, 225 °, 270 °, 315
The displacement amount H of the center P when rotated by an angle (the displacement amount H with respect to the center position P _{0 at} an angle of 0 °) can be obtained in advance.

For example, the center P ₄₅ at a rotation angle of 45 °
The displacement H ₄₅ of

[0042]

H ₄₅ = (T ₄₅ -T ₀ ) / 2 For this reason, for example, when the wafer W is rotated by 45 °, if the wafer W is lowered by H ₄₅ , the center P ₄₅ in the thickness direction of the wafer W is located at the center M of the grinding groove 110.

Therefore, the displacement H of the wafer W at each rotation angle is obtained, and the wafer W is moved up and down so as to cancel the displacement H.
10 in the center M. At this time, the wafer W is linearly moved up or down between the rotation angles to control the movement in the axial direction. That is, FIG.
As shown in (1), the displacement amount H at each rotation angle θ is plotted on a graph, and each point is connected with a straight line. Then, the vertical movement of the wafer W is controlled according to the change of the displacement H.

As described above, the wafer W is rotated once while controlling the vertical movement at the same time as the rotation.
Chamfering is performed over the entire periphery of. Wafer W is 1
When rotated, the drive of the θ-axis motor 96 is stopped, and the rotation of the wafer W is stopped. Next, the Y-axis motor 64 is driven, and the chuck table 100 moves in a direction away from the outer peripheral grinding wheel 108 to return to the origin position. On the other hand, the driving of the outer peripheral motor 104 is stopped, and the rotation of the outer peripheral grinding wheel 108 is stopped.

When the chuck table 100 returns to the home position, the transfer arm 32 receives the wafer W held on the chuck table 100 and carries it to the next cleaning step. As described above, according to the wafer chamfering method of the present embodiment, while controlling the movement of the wafer W in the axial direction such that the center P in the thickness direction of the wafer W is located at the center M of the grinding groove 110. The wafer W is chamfered. As a result, as shown in FIG. 7B, the wafer W having an uneven thickness as shown in FIG. 7A is chamfered uniformly at each point on the peripheral edge. Then, if the wafer W _C thus processed is subjected to a lapping process in a later lapping step, the lapping process is performed so that the wafer W _C is thinned up and down uniformly from a thick portion thereof, as shown by a dotted line in FIG. the can top and bottom surface width C is processed into uniform wafer _{W R (C 1 = C 2} = C 3 = C 4).

As described above, according to the wafer chamfering method of the present embodiment, the peripheral edge of the wafer W can be chamfered evenly in the upper and lower directions. can do. In the present embodiment, the thickness measurement is performed at 45 ° intervals, but the measurement interval is not limited to this. If the measurement interval is narrowed, more precise control becomes possible, and a more precise wafer W can be processed.

Next, a description will be given of a second embodiment of the wafer chamfering method according to the present invention. In the wafer chamfering method of the first embodiment described above, the chuck table 100 is treated as if no run-out occurs.
However, actually, due to the influence of the processing accuracy and the mounting accuracy of the chuck table 100, the outer periphery of the chuck table 100 oscillates when rotated. The run-out of the chuck table 100 directly affects the processing accuracy, and even if the control is performed as in the first embodiment, the run-out of the chuck table 100 causes the center position P of the wafer W to shift. In some cases, accurate control cannot be performed.

Therefore, in the wafer chamfering method of the second embodiment, the movement of the wafer W in the axial direction is controlled while removing the influence of the run-out of the chuck table 100. First, the deflection of the chuck table 100 is measured.
There are the following two methods for measuring the shake. The first method is to directly measure the runout of the chuck table 100. In this method, as shown in FIG. 8A, first, the chuck table 100 located at the origin position is set.
The displacement sensor 200 is installed above the. Then, the chuck table 100 is rotated once, and the displacement amount of the upper surface of the chuck table 100 at this time is measured by the displacement sensor 200. Thus, the runout (= displacement amount) of the outer peripheral portion of the chuck table 100 is measured.

The second method is a method of indirectly measuring the result of grinding the master wafer. In this method, a master wafer having a perfect circular shape and a uniform thickness is chamfered. Then, the deflection of the chuck table 100 is obtained from the surface width of the chamfered master wafer. For example, if the surface width at the grinding start point (point at a rotation angle of 0 °) is C ₀ , the surface width when rotated by 45 ° is C _45, and the angle of the chamfered surface is α (= constant), the runout ζ ₄₅ is the following formula,

[0050]

Ζ ₄₅ = (C ₀ −C ₄₅ ) tan α The runout ζ of the outer periphery of the chuck table 100 is measured by any of the above methods. The measurement was performed at a rotation angle of 45 °, 90 °, 135 °.
°, 180 °, 225 °, 270 °, 315 °. Measurement data of the runout ζ of the outer periphery of the chuck table 100 obtained in this manner is expressed by
When plotted on a graph in which the horizontal axis is the rotation angle θ, FIG.
The graph becomes as shown in FIG.

At the time of chamfering the wafer W, the processing is performed while removing the influence of the shake based on the measurement data of the shake of the outer periphery of the chuck table 100. Specifically, processing is performed as follows. From the measured data shown in FIG. 8 (b), the chuck table 100 by rotating 45 ° from the position of the rotation angle of 0 °, the outer peripheral swings zeta ₄₅ on the upper side. Moreover, by 90 ° rotation from the position of the rotation angle of 0 °, the outer peripheral swings upward zeta _90.

Therefore, 45 degrees from the position of the rotation angle of 0 °
° when rotating the chuck table 100 zeta ₄₅ descends, Moreover, when the rotate 90 °, if the chuck table 100 zeta ₉₀ downward, it is possible to eliminate the influence of vibration. As described above, if the chuck table 100 is moved up and down so as to cancel the shake based on the measurement data of the shake, the influence of the shake can be removed.

Now, as a result of measuring the thickness of the wafer W to be chamfered, the center P in the thickness direction of the wafer W is
Rotation angles 45 °, 90 °, 135 °, 180 °, 225
At positions of 270 ° and 270 °, displacement is made as shown in FIG. 9 (a). Further, the outer circumference of the chuck table 100 has a rotation angle of 45 °, 90 °, 135 °, 180 °.
At positions of °, 225 °, and 270 °, swinging is performed as shown in FIG. 9B.

The center P in the thickness direction of the wafer W is the grinding groove 1
In order to control the chuck table 100 to be positioned at the center M of the chuck table 100, the chuck table 100 is moved in the axial direction by the difference Z between the displacement amount H in the thickness direction of the wafer W at each rotation angle and the swing amount の of the outer periphery of the chuck table 100. Should be moved to For example, at the position of the rotation angle 45 °, the displacement amount H ₄₅ in the thickness direction of the wafer W, if the shake amount of the outer periphery of the chuck table 100 is zeta _45, the difference Z, i.e.,

[0055]

Only Equation 5] Z = H ₄₅ -ζ _45, if caused to lower the chuck table 100 in the axial direction, the center P ₄₅ in the thickness direction of the wafer W is positioned at the center M of the grinding groove 110. The graph of FIG. 9C is a graph in which the difference Z between the displacement amount H and the shake amount ζ is plotted according to each rotation angle θ, and each point is connected by a straight line. If the movement of the chuck table 100 in the axial direction is controlled based on this graph, it is possible to always perform processing in which the center P in the thickness direction of the wafer W is positioned at the center M of the grinding groove 110.

As described above, in the wafer chamfering method of the present embodiment, the processing is performed while removing the influence of the runout of the chuck table 100, so that the processing accuracy is further improved. In this embodiment, the shake is measured at 45 ° intervals, but the measurement interval is not limited to this. If the measurement interval is narrowed, more precise control becomes possible, and a more precise wafer W can be processed.

In the above-described embodiment, the wafer side is moved up and down in the axial direction for control.
The control may be performed by moving the grinding wheel up and down. In the series of embodiments described above, the outer peripheral grinding wheel 10
Although the case where the grinding groove 110 formed in FIG. 8 has a V-shaped cross section has been described, when the shape of the grinding groove has a trapezoidal cross-section, chamfering is performed by the following method.

In general, in the case of chamfering using the outer peripheral grinding wheel 210 having a trapezoidal cross section, the upper and lower sides of the periphery of the wafer W are separately chamfered. That is, as shown in FIG. 10A, the upper peripheral edge is chamfered first, and then, as shown in FIG. 10B, the lower peripheral edge is chamfered. At this time, when chamfering the upper peripheral edge, the upper inclined surface 212 of the groove 212 of the outer peripheral grinding wheel 210 rotated at high speed is used.
When the upper peripheral edge of the wafer W is brought into contact with A and chamfering is performed, and the lower peripheral edge is chamfered, the lower inclined surface 212B of the groove 212 of the outer peripheral grinding wheel 210 rotated at a high speed.
The lower peripheral edge of the wafer W is brought into contact with the wafer W and chamfering is performed.

In the chamfering method of this embodiment, the chamfering is performed such that the distance from the center of the peripheral edge of the wafer in the thickness direction to the inclined surface of the groove of the grindstone is always constant. Specifically, it is as follows. Note that the steps until the wafer W is held on the chuck table 100 are the same as those in the above-described embodiment, and therefore, the steps after the wafer W is held on the chuck table 100 will be described here.

When the wafer W is held on the chuck table 100, a control unit (not shown) performs reference matching based on the measurement result of the thickness sensor 24. That is, the reference is adjusted such that the center P in the thickness direction of the wafer W and the center M of the grinding groove 212 of the outer peripheral grinding wheel 210 match.
This operation is performed as follows. As shown in FIG. 11A, the wafer W immediately after being conveyed from the thickness measurement unit 20 has its center P in the thickness direction shifted from the center M of the grinding groove 212 of the outer peripheral grinding wheel 210. It is held on the chuck table 100.

Here, the thickness T ₀ of the wafer W at an angle of 0 °, that is, at the grinding start point, is known from the measurement result of the thickness sensor 24. From this, the wafer W
It can be seen that the center P ₀ in the thickness direction is located at (T _0/2 ) from the upper surface U of the chuck table 100. On the other hand, the chuck table 100 receives the wafer W in a state where the upper surface U is located at a distance D from the center M of the grinding groove 212 of the outer peripheral grinding wheel 210. Therefore, the center P ₀ in the thickness direction of the wafer W and the outer peripheral grinding wheel 2
The deviation amount δ from the center M of the ten grinding grooves 212 is

[0062]

It can be seen that δ = D− (T _0/2 ). The control device drives the Z-axis motor 94 to raise the chuck table 100 by the distance δ. Thereby, as shown in FIG. 11B, the center P ₀ in the thickness direction of the wafer W is located at the center M of the grinding groove 212 of the outer peripheral grinding wheel 210.

Thus, the reference adjustment of the wafer W is completed. Next, the amount of grinding of the wafer W is adjusted.
That is, the distance from the center P _O in the thickness direction of the wafer W to the upper inclined surface 212A of the grinding groove 212 is positioned such that the predetermined value Q is performed. Here, the center P in the thickness direction of the wafer W coincides with the center M of the grinding groove 212 by the above-described reference alignment, and the distance w from the center M of the grinding groove 212 to the upper inclined surface 212A is Is known.

Therefore, in order for the distance from the center P _O in the thickness direction of the wafer W to the upper inclined surface 212 A of the grinding groove 212 to be the predetermined value Q,

[0065]

## EQU7 ## The wafer W may be raised by F = w-Q. The control device drives the Z-axis motor 94 to thereby control the chuck table 1.
00 is increased by the distance F. As a result, FIG.
As shown in (c), the center P _O in the thickness direction of the wafer W.
Is a predetermined value Q.

As described above, a series of positioning operations is completed, and thereafter, chamfering of the wafer W is started. First, the outer peripheral motor 104 is driven, and the outer peripheral grinding wheel 210
Rotates at high speed. When the rotation of the outer peripheral grinding wheel 210 is stabilized, next, the Y-axis motor 64 is driven, and the wafer W is sent toward the outer peripheral grinding wheel 210.

When the wafer W is fed a predetermined distance, the upper edge of the wafer W comes into contact with the upper inclined surface 212 A of the grinding groove 212. After the contact, the wafer W is sent slowly toward the outer peripheral grinding wheel 210, and as a result, the upper peripheral edge of the wafer W is ground by the outer peripheral grinding wheel 210 and chamfered. The wafer W is fed until the axial distance between the outer peripheral grinding wheel 210 and the wafer W reaches a predetermined set distance. When the inter-axis distance reaches a predetermined distance, the driving of the Y-axis motor 64 is stopped.

When the feed in the Y-axis direction is stopped, then θ
The shaft motor 96 is driven, and the wafer W starts to slowly rotate around the θ axis in the direction opposite to the outer peripheral grinding wheel 210.
As a result, the position of the peripheral edge of the wafer W that contacts the upper inclined surface 212A of the grinding groove 212 changes, and the peripheral edge of the wafer W is chamfered sequentially. However, the wafer W is
Since the thickness varies depending on the position of the peripheral edge, when the wafer W is rotated as described above, the distance from the center P in the thickness direction of the wafer W to the upper inclined surface 212A of the grinding groove 212 changes.

Therefore, the wafer W is moved in the axial direction simultaneously with the rotation of the wafer W, whereby the distance Q from the center P in the thickness direction of the wafer W to the upper grinding groove 212A of the grinding groove 212 is always constant. Control so that Specifically, control is performed as follows. From the measurement results by the thickness sensor 24, the rotation angles 45 °, 90 °, 135 °, 1
The thicknesses T ₄₅ , T ₉₀ , T ₁₃₅ , T ₁₈₀ of the peripheral edge of the wafer W at 80 °, 225 °, 270 °, 315 °
T ₂₂₅ , T ₂₇₀ , T ₃₁₅ are known. Therefore, the wafer W is set at 45 °, 90 °, 135 °, 180 °, and 22 °.
5 °, 270 °, 315 when ° rotated, displacement H ₄₅ of the center _{P, H 90, H 135,} H 180, H 22 5, H 270,
H ₃₁₅ (a displacement amount H with respect to the center position P ₀ when the angle is 0 °) can be obtained in advance.

From this, for example, when the wafer W is
° when rotating is, if the wafer W H ₄₅ is lowered,
The distance Q from the center in the thickness direction of the wafer W to the upper grinding groove 212A of the grinding groove 212 is kept constant. Therefore, when the displacement H of the wafer W at each rotation angle is obtained and the wafer W is moved up and down so as to cancel the displacement H, the distance Q from the center P of the wafer W to the upper inclined surface 212A of the grinding groove 212 is reduced. Grinding can be performed while maintaining a constant value.

At this time, the wafer W is raised or lowered linearly between the rotation angles to control the movement in the axial direction. As described above, the wafer W is rotated once while controlling the vertical movement at the same time as the rotation, and the chamfering is performed over the entire periphery of the upper edge of the wafer W. Then, the lower peripheral edge of the wafer W is chamfered by the same method. In this case, the grinding is performed so that the distance Q from the center P of the wafer W to the lower inclined surface 212B of the grinding groove 212 is constant.

As described above, according to the wafer chamfering method of the present embodiment, the distance Q from the center P in the thickness direction of the wafer W to the upper inclined surface 212A of the grinding groove 212 is determined.
While controlling the movement of the wafer W in the axial direction such that the distance Q from the center P in the thickness direction of the wafer W to the lower inclined surface 212B of the grinding groove 212 is constant. Chamfering. As a result, as shown in FIG. 12, even if the wafer W has an uneven thickness, the chamfering process is performed so that the distance Q from the center P in the thickness direction of the wafer W to the upper and lower chamfered surfaces WC is constant. Is done. If the wafer W _C thus processed is subjected to lapping in a later lapping step, it can be processed into a wafer W _R having a uniform upper and lower surface width C as shown by a dotted line in FIG. _{1 = C 2 = C 3 =} C 4).

As described above, even when the grinding groove 212 of the outer peripheral grinding wheel 210 has a trapezoidal cross section, the wafer is processed as in the above-described embodiment, so that a wafer having a uniform upper and lower surface width can be formed in a later lapping process. Can be processed. In addition,
Also in this case, the above-described grinding groove 11 having a V-shaped cross section is used.
Chuck table 100 in the same manner as the chamfering method using
The movement of the wafer W in the axial direction can be controlled while removing the influence of the runout, thereby enabling more accurate processing.

[0074]

As described above, according to the present invention,
The wafer is processed so that the center in the thickness direction of the wafer is always located at the center of the groove of the grindstone. As a result, even a wafer having a non-uniform thickness can be chamfered evenly up and down. Then, by lapping the processed wafer, a wafer having a uniform upper and lower surface width can be processed.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of a wafer chamfering apparatus.

FIG. 2 is a side view showing a configuration of a processing unit.

FIG. 3 is a plan view showing a configuration of a processing unit.

FIG. 4 is an explanatory diagram of a thickness measuring method.

FIG. 5 is an explanatory view of a method of positioning a wafer in a thickness direction.

FIG. 6 is a graph showing a relationship between a rotation angle θ and a displacement amount H;

FIG. 7 is an explanatory view of the operation of the wafer chamfering method according to the present invention.

FIG. 8 is an explanatory diagram of a method of measuring a runout amount of a chuck table.

FIG. 9 is an explanatory diagram of a wafer chamfering method according to a second embodiment.

FIG. 10 is an explanatory diagram of a chamfering method according to another embodiment.

FIG. 11 is an explanatory diagram of a chamfering method according to another embodiment.

FIG. 12 is a diagram illustrating the operation of the chamfering method according to another embodiment.

FIG. 13 is a side view illustrating a conventional wafer chamfering method.

FIG. 14 is a diagram illustrating the operation of a conventional wafer chamfering method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Wafer chamfering apparatus 20 ... Thickness measurement part 22 ... Measurement table 24 ... Thickness sensor 30 ... Transport part 32 ... Transfer arm 40 ... Processing part 100 ... Chuck table 108 ... Peripheral grinding grindstone 110 ... Grinding groove M ... Grinding groove Center P: Center of wafer in thickness direction W: Wafer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3C034 AA01 BB01 BB14 BB73 BB83 BB92 CA04 CB01 CB07 CB14 DD13 3C049 AA03 AA16 AB03 AB04 AB06 AC02 BA07 BA13 BB02 BC01 CA01 CB01 CB03

Claims (8)

[Claims] 1. A grindstone having a V-shaped cross section formed on a peripheral surface thereof is rotated, and a peripheral edge of a wafer held on a chuck table is brought into contact with the groove to rotate the grindstone. In the wafer chamfering method for chamfering, the center in the thickness direction of the peripheral edge of the wafer abutting on the groove of the grinding stone is located at the center of the groove of the grinding stone, relative to the axial direction of the grinding stone and the wafer A wafer chamfering method, wherein the wafer is rotated while adjusting a proper position. 2. The thickness of the periphery of the wafer to be chamfered is measured at predetermined angles, a center position in the thickness direction of the periphery of the wafer at each measurement point is calculated, and based on the calculation result, 2. The wafer chamfering method according to claim 1, wherein the center of the peripheral edge of the wafer in the thickness direction is located at the center of the groove of the grindstone by relatively moving the wafer in the axial direction. 3. A displacement amount of an outer periphery of the chuck table with respect to a predetermined reference plane is measured at predetermined angles, and based on the measurement result and the calculation result, the grindstone and the wafer are relatively moved in the axial direction. 3. The wafer chamfering method according to claim 2, wherein the center of the peripheral edge of the wafer in the thickness direction is positioned at the center of the groove of the grindstone by moving the wafer. 4. A master wafer having a uniform thickness is held by the chuck table, and the center of the master wafer in the thickness direction is aligned with the center of the groove of the grindstone. The peripheral edge of the master wafer is chamfered by rotating the peripheral edge of the master wafer in contact with the groove, and the surface width of the chamfered master wafer is measured at predetermined angles, and the surface width is measured. 4. The wafer chamfering method according to claim 3, wherein an amount of displacement of the outer periphery of the chuck table is obtained by calculating from a result. 5. A grindstone having a groove with a trapezoidal cross-section formed on the peripheral surface is rotated, and one edge of the wafer held by the chuck table is brought into contact with the inclined surface on one side of the groove and rotated. By chamfering one peripheral edge of the wafer, the other peripheral edge of the wafer held on the chuck table is brought into contact with the inclined surface of the other side of the groove and rotated, thereby rotating the wafer. In a wafer chamfering method for chamfering the periphery of the other side and chamfering the periphery of the wafer, such that a distance from a center in a thickness direction of the periphery of the wafer to an inclined surface of the groove of the grindstone is constant. A method of chamfering a wafer, comprising rotating the wafer while adjusting the relative position of the grinding wheel and the wafer in the axial direction to chamfer both sides of the periphery of the wafer. . 6. The thickness of the periphery of the wafer to be chamfered is measured at predetermined angles, a center position in the thickness direction of the periphery of the wafer at each measurement point is calculated, and based on the calculation result, 6. The method according to claim 5, wherein a distance from a center in a thickness direction of a peripheral edge of the wafer to an inclined surface of a groove of the grindstone is made constant by relatively moving the wafer and the wafer in the axial direction. Wafer chamfering method. 7. A displacement amount of an outer periphery of the chuck table with respect to a predetermined reference plane is measured at predetermined angles, and based on the measurement result and the calculation result, the grindstone and the wafer are relatively moved in the axial direction. 7. The wafer chamfering method according to claim 6, wherein a distance from a center of a peripheral edge of the wafer in a thickness direction to an inclined surface of a groove of the grindstone is made constant by moving the wafer. 8. A master wafer having a uniform thickness is held by the chuck table, and a center of the master wafer in a thickness direction is positioned at a fixed distance from an inclined surface of a groove of the grinding stone. The peripheral edge of the master wafer is brought into contact with the groove of the grindstone to be rotated and chamfered, and the surface width of the chamfered master wafer is measured at predetermined angle intervals. 7. The wafer chamfering method according to claim 6, wherein a displacement amount of an outer periphery of the chuck table is obtained by calculating from a measurement result of the surface width.